Wireless telephony technology continues to evolve over time. Most recently, the European Telecommunications Standards Institute (ETSI) has promulgated a new standard for mobile telephony service, known as “Universal Mobile Telecommunications Service” or UMTS which offers broadband, packet-based transmission of voice, text, video and multimedia information at rates as high as 2 Mbs. The proposed UMTS standard describes a wireless network that includes one or more radio access nodes, each typically referred to as a “Node B.” One or more Radio Network Controllers (RNC) exist within the UMTS network to manage the radio access nodes. Each RNC has a broadband connection, typically in the form of an Asynchronous Transport Mode (ATM) Link, to a UMTS core network that provides Authorization, Authentication and Accounting (AAA) Functions.
Advances in the field of wireless LAN technology have resulted in the emergence of publicly accessible wireless LANs (e.g., “hot spots”) at rest stops, cafes, libraries and similar public facilities. Presently, wireless LANs offer mobile communications device users access to a private data network, such as a Corporate Intranet, or a public data network such as the Internet. The relatively low cost to implement and operate a wireless LAN, as well as the available high bandwidth (usually in excess of 10 Megabits/second) makes the wireless LAN an ideal access mechanism through which the mobile communications device user can exchange packets with an external entity.
Given the lower access cost and higher bandwidth afforded by wireless LANs, users of mobile communications devices often find it advantageous to transition from a wireless telephony network, such as the UMTS network, to a wireless LAN. To that end, many present day wireless LAN operators provide coverage areas that overlap the coverage area of a UMTS network. Also, many mobile communication device manufacturers will include a dual protocol stack within the device to enable the device user to transition between networks.
Ideally, transitioning from the wireless telephone network to the wireless LAN (and vice versa) should occur seamlessly, i.e., without any loss of communications. To achieve a seamless transition from a UMTS network to the wireless LAN, the mobile communications device must first detect entry into the coverage area of the wireless LAN before undertaking a handoff from the wireless telephony network to the wireless LAN. Presently, the mobile communications device undertakes detection of a wireless LAN by operating a second receiver tuned to the wireless LAN while a first receiver remains tuned to the wireless telephony network. Continuously operating both the first and second receivers concurrently consumes battery resources in the mobile communications device, often a precious commodity.
Thus, there is a need for a technique for enabling a mobile communications device to seamlessly transition from one wireless network to another while overcoming the aforementioned disadvantage of the prior art.